Typical active optical detection systems, such as a laser range finder, may transmit a light pulse and receive a reflection of the light pulse in response. The active optical detector may determine a range to an object, e.g. the source of the reflection, based on the time of flight of the light pulse. The time of flight may be measured as the elapsed time from the transmission of the light pulse to the receipt of the reflection the light pulse. The range or distance may be calculated by dividing the time of flight by two times the speed of light. The range determinations may be used for proximity detection and, in an instance in which two or more light pulses have been received, for determination of object velocity. Some active optical detectors may be susceptible to confusion, e.g. erroneous results, from soft objects, such as rain, snow, fog, dust, smoke, or the like. The light pulse may be reflected by the soft objects, causing erroneous range measurements. Although, some active optical detectors may provide accurate range measurements, they cannot determine a direction of the object in relation to the active optical detector.
In some cases active optical detectors using a laser may have a high peak power which may limit the achievable accuracy of the active optical detector without exceeding power limits, such as determined by eye-safety standards. In an instance in which the pulse transmission is 1 ns the accuracy of the typical active optical detector may be about 1 ft. The typical active optical detector may also be limited to laser light sources, such as high power lasers, which do not dissipate over a short range, may be tuned to a specific wavelength for detection, or the like. These high powered lasers may be expensive and, in some instances, dangerous to the human eye.